Friction stir welding apparatus

ABSTRACT

The apparatus includes a base  23  fixed at a predetermine position, a tool holding jig  29 , to which a welding tool  21  is mounted, installed on the base  23  rotatably about a preset reference axis L 1  and movably along the reference axis L 1 , a tool rotation driving means for rotating the tool holding jig about the reference axis L 1 , and a tool movement driving means for moving the tool holding jig along the reference axis L 1 . The apparatus realizes miniaturization of the apparatus, simplification of the structure, and improvement of the operability.

TECHNICAL FIELD

The present invention relates to a friction stir welding apparatus forwelding an object by a friction stir welding and more particularly to afriction stir welding apparatus suitably used for welding an object by aspot friction stir welding.

BACKGROUND ART

FIG. 25 is a drawing showing a friction stir welding apparatus 1 of theconventional art. The friction stir welding apparatus 1 includes awelding device 2 performing a welding operation and an arm 3 connectedto the welding device 2 for positioning the welding device 2 for anobject 4 to be welded. The welding device 2 is equipped with a toolholding jig 7 installed rotatably about a reference axis L1 and movablyalong the reference axis L1, a rotation motor for rotating the toolholding jig 7, and a displacement motor for moving the tool holding jig7 along the reference axis L1. On the tool holding jig 7, a columnarwelding tool 5 is mounted. The arm 3 may be made by a multi-joint robotand a tip 6 of the arm 3 is connected to the welding device 2.

The conventional friction stir welding apparatus 1 moves the weldingdevice 2 toward the object 4 by the arm 3. Next, the apparatus 1operates the welding tool 5 mounted to the tool holding jig 7 to rotateand make contact with the object 4. By doing this, frictional heat isgenerated in the object 4. The friction stir welding apparatus 1 makesthe object 4 fluid by the frictional heat, stirs the object 4, and mixesand welds the boundary parts of two members 4 a and 4 b constituting theobject 4 to be welded.

The aforementioned welding method using frictional heat is calledfriction stir welding (abbreviated to “FSW”).

Conventionally, an object to be welded by the friction stir welding is alarge object. Therefore, without moving a large object 4, it is weldedby moving the welding device 2 by the arm 3.

The welding device 2 includes a rotation motor and a pressure motor.Therefore, the weight thereof is large such as about 120 kg. The arm 3must be highly rigid in order to support the welding device 2. Further,when the moving distance of the welding device 2 is long, the arm 3 mustbe long. As mentioned above, in the friction stir welding apparatus 1,it is required to make the arm long and highly rigid, thus the necessaryspace occupied by the arm 3 is wider than that occupied by the weldingdevice 2. Therefore, a problem arises that the structure becomesinevitably large. Further, in the friction stir welding apparatus 1, amoving space for the welding device 2 to move to the object 4 isrequired, so that a problem arises that a sufficiently large space forinstallation is necessary.

Further, the whole structure of the friction stir welding apparatus iscomplicated due to the arm 3, thereby, a problem arises that themaintenance and adjustment are difficult. Further, according to theshape of the object 4, an operator should perform both the teachingoperation and the exchange operation of a welding tool, thereby, aproblem arises that the workability is lowered.

Therefore, the present invention is intended to provide a friction stirwelding apparatus which has a simple constitution and a goodoperability, and can be miniaturized.

DISCLOSURE OF INVENTION

The friction stir welding apparatus of the present invention comprises:a base fixed at a predetermine position; a tool holding jig to which awelding tool is mounted, the tool holding jig being installed on thebase rotatably about a reference axis and movably along the referenceaxis; tool rotation driving means for rotating the tool holding jigabout the reference axis; and tool movement driving means for moving thetool holding jig along the reference axis.

According to the present invention, an object to be welded is positionedon the base fixed at the predetermined position and the welding tool ismounted on the tool holding jig. In this state, the holding jig isrotated about the reference axis and moved along the reference axis. Thewelding tool mounted on the tool holding jig is driven together with thetool holding jig, thus the welding tool rotates and makes contact withthe object to be welded. By doing this, frictional heat is generated onthe object to be welded, and the object is made fluid, and the weldingtool is buried in the object. When the welding tool is buried up to theneighborhood of the respective boundary parts of a plurality of membersconstituting the object to be welded, the fluid boundary parts can berespectively stirred and mixed. By doing this, the plurality of membersconstituting the object to be welded can be welded to each other.

When the base is fixed and the object to be welded is positioned on thebase like this, the aforementioned arm which is necessary in theconventional art becomes unnecessary. By doing this, the apparatus canbe miniaturized, and the structure thereof can be simplified, thus themanufacturing cost can be reduced. Further, the base does not move sothat the installation space can be made smaller.

As mentioned above, a friction stir welding apparatus which isinexpensive and occupies only a small installation space can bestructured, so that even a user who is short of funds and has only asmall installation space such as a small and medium-sized enterprise canintroduce the friction stir welding apparatus.

Further, since the base is fixed, the teaching operation of adjustingthe moving position of the base is not required and the exchangeoperation of the welding tool can performed easily. By doing this, thefriction stir welding apparatus, even when object to be welded arelow-volume and high-variety products, can prevent the workability fromlowering. Further, vibration of the tool holding jig, which could becaused when the base is moved, can be eliminated. Further, for example,an operator positions an object to be welded, thereby can weld theobject at any optional position, can easily change the welding positionaccording to the abject to be welded, and can flexibly respond accordingto the object to be welded.

Further, as long as the tool rotation driving means and the toolmovement driving means transfer drive force to the tool holding jig,there is no need to install all of the tool rotation driving means andthe tool movement driving means on the base. Therefore, a part of thetool rotation driving means and the tool movement driving means can beinstalled separately from the base, thus they can be designed easily.Further, the base is fixed without moving, so that there is a littlelimit to the designed weight.

Further, it is preferable that the friction stir welding apparatus ofthe present invention further comprises positioning means, which isinstalled on the base, for positioning an object to be welded withrespect to the reference axis.

According to the present invention, an object to be welded is positionedwith respect to the reference axis by the positioning means. By doingthis, the object to be positioned on the base can be prevented fromdisplacement and the positioning operation of the object to be weldedcan be performed surely and simply.

For example, when an object to be welded is to be moved by an operator,there is the possibility that the object is shifted from the position tobe positioned. However, since the positioning means is installed, thedisplacement of the object to be welded can be prevented. By doing this,the object to be welded can be correctly positioned, and the timerequired for positioning the object to be welded can be shortened, andthe number of objects to be welded per unit time can be increased.

Further, in the friction stir welding apparatus of the presentinvention, it is preferable that the positioning means positions holdingmeans for holding the object to be welded with respect to the base.

According to the present invention, the holding means is positioned onthe base by the positioning means, thus the object to be welded ispositioned with respect to the reference axis. Therefore, even an objectwhich is difficult to be positioned can be easily positioned bypositioning in the state that it is held by the holding means.

Further, when the welding operation is performed in the state that theobject to be welded is held, the object can be prevented from shifting,displacing and deforming during welding. By doing this, the weldingquality of the object can be improved.

Further, when the welding tool rotates and makes contact with the objectto be welded, force for moving the object is applied and there is thepossibility that the object may be raised to high temperature due tofrictional heat. When the welding operation is performed in the statethat the object is held by the holding means, the operator himself doesnot need to hold the object to be welded. By doing this, the danger ofcontact of the operator himself with the rotation tool during rotationis eliminated, thus the safety can be improved. Further, even when it isdifficult for the operator himself to hold the object to be welded, theoperator himself does not need to hold the object by the holding meansand the convenience can be enhanced.

Further, it is preferable that the friction stir welding apparatus ofthe present invention further comprises holding means, which isinstalled on the base, for holding an object to be welded.

According to the present invention, the welding operation is performedin the state that an object to be welded is held by the holding meansinstalled on the base. The holding means installed on the base holds theobject to be welded on the base. The welding operation is performed inthe state that the object to be welded is held on the base, thus theobject can be prevented from shifting, displacing and deforming duringwelding. By doing this, the welding quality of the welded part can beimproved.

Further, when the welding tool rotates and makes contact with the objectto be welded, force for moving the object is applied and there is thepossibility that the object may be raised to high temperature due tofrictional heat. When the welding operation is performed in the statethat the object to be welded is held by the holding means, the operatordoes not need to hold the object and the convenience can be enhanced.

Further, in the friction stir welding apparatus of the presentinvention, it is preferable that the holding means has a backing memberfor supporting a part of the object located on the reference axis from aside opposite to the welding tool.

According to the present invention, the welding tool rotates and makescontact with the object to be welded in the state that the object issupported by the backing member. Even if the part of the object on thereference axis is pressed by the welding tool, the back side part of thepart pressed by the welding tool is supported by the backing member, sothat it is prevented from deformation. By doing this, defective weldingdue to deformation of the object to be welded can be prevented and thewelding quality can be improved.

Further, in the friction stir welding apparatus of the presentinvention, it is preferable that the holding means comprises: a firstclamping piece installed movably along the reference axis with respectto the base and the tool holding jig; clamping piece movement drivingmeans for moving the first clamping piece along the reference axis; asecond clamping piece for holding the object cooperatively with thefirst clamping piece, the second clamping piece being installed so thatthe second clamping piece can move along the reference axis from aprojection position projecting over the backing member and a retractionposition retracting with respect to the backing member; and spring forcegeneration means for giving spring force toward the projection positionto the second clamping piece.

According to the present invention, in the state that an object to bewelded is arranged on the second clamping piece at the projectionposition, the first clamping piece is moved and driven toward the secondclamping piece by the clamping piece driving means. By doing this, theinterval between the first clamping piece and the second clamping pieceis narrowed and the first clamping piece makes contact with the objectto be welded. Furthermore, when the first clamping piece is moved anddriven toward the backing member against the spring force given to thesecond clamping piece, the object to be welded can be clamped by thefirst clamping piece and second clamping piece.

In the state that the object to be welded is clamped by the first andsecond clamping pieces, the first clamping piece is additionally movedtoward the backing member, thus the object to be welded can be movedtoward the backing member and the object can be supported by the backingmember.

In the state that the object to be welded is clamped by the first andsecond clamping pieces like this, when the welding operation isperformed, the welding operation can be performed in the state that theobject to be welded is held. Further, when the object to be welded issupported by the backing member, the welding operation can be performedin the state that the object to be welded is prevented from deformation.By doing this, the object to be welded can be prevented from deformationand displacement during welding and the welding quality can be improved.Further, when the welding is finished, the clamping piece driving meansis operated so as to separate the first clamping piece from the object,thus the first clamping piece is separated from the second clampingpiece, and the object can be easily released from the holding state. Theholding and release of the object can be easily switched like this andthe welding operation can be performed in a short time.

Further, in the friction stir welding apparatus of the presentinvention, it is preferable that the first clamping piece is formed sothat a center axis thereof is coaxially with the reference axis; thesecond clamping piece is formed so that a center axis thereof iscoaxially with the reference axis; and the object is clamped by an endface of the first clamping piece and an end face of the second clampingpiece.

Further, it is preferable that the first clamping piece and the secondclamping piece are formed in a cylindrical or hollow shape,respectively.

Further, in the friction stir welding apparatus of the presentinvention, it is preferable that the backing member is installed movablyalong the reference axis; and backing member movement driving means formoving the backing member along the reference axis is installed in placeof the tool movement driving means.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing the friction stir welding apparatusas an embodiment of the present invention.

FIG. 2 is a drawing schematically showing the stir welding operationusing the friction stir welding apparatus shown in FIG. 1.

FIG. 3 is a block diagram showing the electrical constitution of thefriction stir welding apparatus shown in FIG. 1.

FIG. 4 is a flow chart showing the operation procedure of the controlmeans of the friction stir welding apparatus shown in FIG. 1.

FIG. 5 is a flow chart showing the operation procedure of the controlmeans of the welding operation of the friction stir welding apparatusshown in FIG. 1.

FIGS. 6A and 6B are sectional views for explaining the procedure of thewelding operation of the friction stir welding apparatus shown in FIG.1.

FIGS. 7A, 7B, and 7C are sectional views for explaining the procedure ofthe welding operation of the friction stir welding apparatus shown inFIG. 1.

FIG. 8 is a flow chart showing the operation procedure of the controlmeans of the welding position confirmation operation of the frictionstir welding apparatus shown in FIG. 1.

FIG. 9 is a drawing showing another operation configuration of thefriction stir welding apparatus shown in FIG. 1.

FIG. 10 is a drawing showing still another operation configuration ofthe friction stir welding apparatus shown in FIG. 1.

FIG. 11 is a side view showing the friction stir welding apparatus ofanother embodiment of the present invention.

FIG. 12 is a plan view showing the friction stir welding apparatus shownin FIG. 11.

FIG. 13 is a perspective view showing the friction stir weldingapparatus of still another embodiment of the present invention.

FIG. 14 is a perspective view showing the holding jig mounted on thefriction stir welding apparatus shown in FIG. 13.

FIG. 15 is a perspective view showing another example of the holding jigmounted on the friction stir welding apparatus shown in FIG. 13.

FIG. 16 is a perspective view showing the clamping part of the holdingjig shown in FIG. 15.

FIG. 17 is a perspective view showing the friction stir weldingapparatus shown in FIG. 13 in the state that the holding jig shown inFIG. 15 is mounted.

FIG. 18 is a sectional view viewed from the section line S-S shown inFIG. 17.

FIG. 19 is a perspective view showing still another example of theholding jig mounted on the friction stir welding apparatus shown in FIG.13.

FIG. 20 is a perspective view showing the friction stir weldingapparatus of a further embodiment of the present invention.

FIG. 21 is a sectional view showing the enlarged neighborhood of thetable of the friction stir welding apparatus shown in FIG. 20.

FIGS. 22A, 22B, and 22C are sectional views showing the operation of theholding means shown in FIG. 21.

FIGS. 23A and 23B are sectional views showing the holding means of acomparison example different from the embodiment of the presentinvention.

FIG. 24 is a block diagram showing the electrical constitution of thefriction stir welding apparatus as a modification of the aforementionedembodiment.

FIG. 25 is a drawing showing the friction stir welding apparatus of theprior art.

BEST MODE FOR CARRYING OUT THE INVENTION

A friction stir welding apparatus 20 as an embodiment of the presentinvention which are shown in FIGS. 1 and 2, in the state that an objectto be welded 22 is positioned on a base 23 by an operator, is anapparatus of frictionally stirring and welding the object 22, which isparticularly used in spot welding. For example, the friction stirwelding apparatus 20 is used to manufacture thin and medium-thinaluminum products and it is used to manufacture car bodies, boxes,design structures, and other stacked objects to be welded.

The friction stir welding apparatus 20 makes a columnar welding tool 21rotate and come into contact with the object 22, presses the sameagainst the object 22, and causes frictional heat between the weldingtool 21 and the object 22. Next, the friction stir welding apparatus 20makes the object 22 fluid by frictional heat and buries the welding tool21 into the object 22. The welding tool 21 is buried up to theneighborhood of the respective boundary parts of a plurality of members22 a and 22 b to be welded constituting the object 22. In this state,the welding tool stirs the fluid object 22, thereby mixes the boundaryparts of the members 22 a and 22 b, and welds the members 22 a and 22 bto each other.

The base 23 of the friction stir welding apparatus 20 is installed in apredetermined position. The base 23 includes a head 24 for installing atool holding jig 29 on which the welding tool 21 is removably mounted, atable 25 installed opposite to the head 24 at some interval, a column 26for supporting both the head 24 and the table 25, and a base part 27connected to the column 26 and fixed at the installation position.

According to this embodiment, the base part 27 is fixed to theinstallation part of a floor 30 which is a fixed position. Further, thecolumn 26 is extended from the base part 27 upward vertically. Further,the head 24 and the table 25 are projected horizontally from the column26.

The tool holding jig 29 installed in the head 24 is installed rotatablyabout a predetermined reference axis L1 and is installed movabily anddrivably along the reference axis L1. For example, the predeterminedreference axis L1 is extended vertically and passes the center axis ofthe tool holding jig 29. The head 24 has a drive force transfermechanism for driving the tool holding jig 29 and drive force from atool rotation driving means 34 (FIG. 3) and a tool movement drivingmeans 35 (FIG. 3), which will be described later, is given to the toolholding jig 29.

The table 25 has an opposing face 31 which is perpendicular to thereference axis L1 and opposite to the tool holding jig 29. Further, inthe table 25, a backing member 32 projecting from the opposing face 31toward the tool holding jig 29 is formed. The backing member 32, forexample, is formed in a cylindrical shape and the center axis thereof isarranged coaxially with the reference axis L1.

On the friction stir welding apparatus 20, the tool rotation drivingmeans 34 for rotating the tool holding jig 29 about the reference axisL1 and the tool movement driving means 35 for moving the tool holdingjig 29 along the reference axis L1 are installed. In this embodiment,the driving means 34 and 35 are built in the base 23, and for example,they are made so as to include a servo motor. The driving means 34 and35 drive the tool holding jig 29 via a drive force transfer mechanisminstalled in the head 24.

Further, the friction stir welding apparatus 20 is equipped with acontroller 38 including an input unit 36 for inputting weldingconditions for frictional stirring and welding and a display unit 37 fordisplaying the welding conditions and an operation pedal 39 foroutputting a welding start instruction from an operator. The input unit36 has a plurality of buttons 36 a. The input unit 36, when the buttons36 a are operated, outputs conditions given by the operator.

The controller 38 is installed in a position where an operator caneasily operate and recognize. For example, the controller 38 isinstalled in the neighborhood of the base 23 and when he is to performthe welding operation, it is installed within his reach when hestretches his arm during his welding operation and at a position awayfrom the displacement area of the welding tool 29 where there is nodanger even if he operates the input unit 36 during his weldingoperation.

Further, the controller 38 has an indicating means 45 for indicating theoperation state of the friction stir welding apparatus. The indicatingmeans 45, for example, includes an end lamp 42 lighting when the weldingoperation ends, an error lamp 43 lighting when a welding operation erroris caused, and a speaker 44 sounding the welding operation state.

Further, the operation pedal 39 has a bottom 40 installed on the floor30 and a plate-shaped foot-operated lever 41 installed verticallymovably. The foot-operated lever 41 is given spring force applied upwardby a spring. The operation pedal 39, when the foot-operated lever 41 isstepped on by an operator and is moved downward, outputs a welding startinstruction signal. Further, when he releases his foot from thefoot-operated lever 41, it is moved upward and the welding startinstruction signal is outputted.

FIG. 3 is a block diagram showing the electrical constitution of thefriction stir welding apparatus 20. The friction stir welding apparatus20 additionally has a control means 46 for controlling the respectivemeans constituting the friction stir welding apparatus 20.

The tool rotation driving means 34, on the basis of a signal given fromthe control means 46, decides the rotational speed and rotational timeand rotates the tool holding jig 29. Further, the tool rotation drivingmeans 34 detects load torque necessary to rotate the tool holding jig 29at a predetermined rotational speed and gives a signal indicating theload torque to the control means 46. The load torque is obtained, forexample, on the basis of a load current flowing in the rotation motorconstituting the tool rotation driving means 34. Further, the toolrotation driving means 34 may give a signal indicating the state underwelding, for example, the rotational speed to the control means 46. Thecontrol means 4 may give the rotational speed during the weldingoperation and the load torque to the display unit 37 to display thevalues.

The tool movement driving means 35, on the basis of a signal given fromthe control means 46, decides the moving speed and moving time and movesthe tool holding jig 29. Further, the tool movement driving means 35detects load torque necessary to move the tool holding jig 29 at apredetermined moving speed and gives a signal indicating the load torqueto the control means 46. The load torque is obtained, for example, onthe basis of a load current flowing in the movement motor constitutingthe tool movement driving means 35. Further, the tool movement drivingmeans 35 may give a signal indicating the state under welding, forexample, the moving speed to the control means 46. The control means 4may give the moving speed during the welding operation and the loadtorque to the display unit 37 to display the values.

The input unit 36 outputs the welding conditions relating to thefriction stir welding operation inputted from the operator and gives itto the control means 46. Further, the control means 46 gives the weldingconditions to the display unit 37 to display them. Tables 1 and 2indicate examples of the welding conditions.

TABLE 1 Welding time Rotational (s) Pressure (N) Speed (rpm) 1st stage0.5 4000 3000 condition 2nd stage 1.0 3500 2500 condition 3rd stage 0.32000 3000 condition

TABLE 2 Welding time Descending Rotational (s) Speed (m/s) Speed (rpm)1st stage 0.5 5.0 3000 condition 2nd stage 1.0 0.5 2500 condition 3rdstage 0.3 0.0 3000 condition

For example, as indicated in Table 1, the welding conditions includethree conditions such as welding time, pressure, and rotational speed.Further, as indicated in Table 2, in place of the pressure, thedescending speed of the tool holding jig 29 may be defined as acondition.

The welding time is the time required for the tool holding jig 29 torotate at a preset pressure or descending speed and a preset rotationalspeed. The pressure is the pressure for pressing the tool holding jig 29toward the backing member 32 and the descending speed is the speed ofthe tool holding jig 29 moving toward the backing member 32. Therotational speed is the speed of the tool holding jig 29 to rotate aboutthe axis and for example, it is set by the number of revolutions perminute.

As indicated in Tables 1 and 2, the welding conditions can be at amultistage. Namely, in the course of time, the pressure, descendingspeed, and rotational speed can be set changeably.

Further, after welding, the speed of the tool holding jig 29 to separatefrom the object 22 and the rotational speed at that time may be input.

Table 3 shows an example of the plate thickness of the object to bewelded 22. Further, the plate thickness of the object 22 may be inputtedfrom the input unit 36 to the control means 46. As conditions of theobject to be welded 22, for example, when three members are to bewelded, the thickness of the upper plate on the side of the tool holdingjig 29; the thickness of the medium plate neighboring the upper plate onthe side of the backing member 32, and the thickness of the lower plateneighboring the medium plate on the side of the backing member 32 may beinputted to set the total plate thickness of the object to be welded 22.However, the number of members constituting the object 22 is not limitedto three and the total plate thickness of the object 22 is set accordingto the number of members.

TABLE 3 Upper plate Medium plate Lower plate Total plate thicknessthickness thickness thickness (mm) (mm) (mm) (mm) Object to be 1.0 1.21.2 3.4 welded

Table 4 indicates the pin shape of the welding tool 21. Further, theshape of the welding tool 21 may be inputted from the input unit 36 tothe control means 46. For example, the welding tool 21, as shown inFIGS. 6A and 6B, has a tool body 50, which is formed in a columnar shapeand has a flat shoulder face 52 at its end, and a columnar pin 51projected from the shoulder face 52. The center axis of the tool body 50and the center axis of the pin 51 are positioned coaxially. Table 4indicates the pin shape of the welding tool 21. For example, the pinlength end pin diameter of the welding tool 21 as indicated in the tableare set.

TABLE 4 Pin length (mm) Pin diameter (mm) Welding tool 2.5 3.0conditions

The control means 46 may have a memory for storing the weldingconditions. For example, any of a plurality of welding conditions storedin the memory beforehand is selected by an operator and on the basis ofthe selected welding condition, the control means 46 may control theother respective means.

Further, the operation pedal 39 outputs a welding start instructionsignal and welding stop instruction signal to the control means 46. Thecontrol means 46, on the basis of the signals given from the operationpedal 39 and signals given from the tool driving means 34 and 35,controls the indicating means 45. Concretely, the control means 46 turnson and off the end lamp 42 and the error lamp 43 and sounds theoperation state from the speaker 44.

FIG. 4 is a flow chart showing the operation procedure of the controlmeans 46. When the preparations for friction stir welding, such asmounting the welding tool 21 to the tool holding jig 29, are set up, thecontrol means 46 goes to Step a1 and starts the operation.

At Step a1, the control means 46 is given the conditions for friction.stir welding from the input unit 36. The control means 46 generatesinstruction signals for operating the tool rotation driving means 34 andthe tool movement driving means 35 according to the welding conditionsand goes to Step a2.

At Step a2, the control means 46 judges whether a welding startinstruction signal is given from the operation pedal 39 or not. When thewelding start instruction signal is given, the control means 46 judgesthat the operator is ready for operation and goes to Step a3,

At Step a3, the control means 46 gives a signal generated according tothe welding conditions to the tool rotation driving means 34 and thetool movement driving means 35, starts the welding operation by thedriving means 34 and 35, and goes to Step a4.

At Step a4, the control means 46 judges whether a welding stopinstruction signal is given from the operation pedal 39 or not. When thewelding stop instruction signal is given, the control means 46 judgesthat the operator is separated from the neighborhood of the apparatusand goes to Step a10. Further, when the welding stop instruction signalis not given, the control means 46 goes to Step a5.

At Step a5, the control means 46, on the basis of the set weldingoperation time, judges whether the welding operation is finished or not.When the control means 46 judges that the welding operation is notfinished, it goes to Step a4.

The control means 46, until it judges that the welding operation iscompleted, repeats Steps a4 and a5 and when it judges that the weldingoperation is completed, it goes to Step a6.

At Step a6, the control means 46 controls the end lamp 42 so as to lightand goes to Step a7.

At Step a7, when the welding stop instruction signal is given from theoperation pedal 39, the control means 46 judges that the operatorfinishes the welding operation and goes to a8.

At Step a8, the control means 46 controls the end lamp 42 so as to goout. When the end lamp 42 goes out, the control means goes to Step a9.

At Step a9, the control means 46 ends the operation.

Further, at Step a4, when the welding stop instruction signal is givenfrom the operation pedal 39 during the welding operation, the controlmeans 46 judges that the operator is separated from the neighborhood ofthe apparatus and goes to Step a10. At Step a10, the control means 46gives a signal indicating emergency stop to the tool rotation drivingmeans 34 and the tool movement driving means 35, stops the tool holdingjig 29 in an emergency, and goes to Step a11.

At Step a11, the control means 46 controls the error lamp 43 so as tolight and goes to Step a12.

At Step a12, to move the tool holding jig 29 to the initial position,the control means 46 gives a drive signal to the tool rotation drivingmeans 34 and the tool movement driving means 35, moves the welding tool21 to the initial position, and goes to Step a13.

At Step a13, the control means 46 controls the error lamp 43 so as to goout. When the error lamp 43 goes out, the control means goes to Step a9.

At Step a9, the control means 46 ends the operation.

FIG. 5 is a flow chart showing the operation procedure of the controlmeans of the welding operation. Further, FIGS. 6A and 6B and FIGS. 7A,7B, and 7C are sectional views for explaining the procedure of thefriction stir welding operation and the operation proceeds in the orderof FIGS. 6A, 6B, 7A, 7B, and 7C.

The control means 46 instructs start of the welding operation at Step a3aforementioned and at Step a5, it judges whether the welding operationis finished or not. The operation during this period, that is, theoperation of the control means 46 in the welding operation will beexplained by referring to FIGS. 6A and 6B and FIGS. 7A, 7B and 7C.

The control means 46, when it judges that the welding operation isstarted at Step b0, goes to Step b1 and starts the welding operation.

At Step b1, on the basis of the welding conditions, the control means 46gives a signal to the tool rotation driving means 34 so as to rotate thetool holding jig 29. The control means 46 rotates the tool holding jig29 and goes to Step b2.

At Step b2, on the basis of the welding conditions, the control means 46gives a signal to the tool movement driving means 35 so as to bring thetool holding jig 29 close to the backing member 32. The control means46, when the tool holding jig 29 is moved, as shown in FIG. 6A, movesthe welding tool 21 toward the object to be welded 22 in the state thatit is rotated and goes to Step b3.

At Step b3, as shown in FIG. 6B, at the time when the end of the weldingtool 21 mounted on the tool holding jig 29 is presumed to make contactwith the object 22, or when the end of the welding tool 21 is presumedto reach the position where the end of the welding tool 21 makes contactwith the object 22, the control means 46 judges whether the object 22and the end of the pin 51 of the welding tool 21 make contact with eachother or not.

For example, the control means 46, on the basis of the weldingconditions, calculates the time or displacement position where it ispresumed that the welding tool will make contact with the object to bewelded 22. Further, the control means 46, on the basis of a signalindicating the load torque of the driving means 34 and 35, judges thatthe object 22 and the welding tool 21 make contact with each other.Further, the control means 46 may judge the contact state on the basisof a signal given from a contact sensor for judging that the object 22and the welding tool 21 make contact with each other. The control means46 goes to Step b4 when it judges that the welding tool 21 makes contactwith the object 22.

At Step b4, on the basis of the welding conditions, the control means 46operates the tool rotation driving means 34 and the tool movementdriving means 35. The control means 46, on the basis of the weldingconditions, gives a signal to the tool driving means 34 and 35 andburies the welding tool 21 into the object 22.

As shown in FIG. 7A, the welding tool 21 rotates while making contactwith the object 22, thereby generates friction heat. The welding tool 21forms a fluid part 53 in the object 22 by making it fluid by frictionalheat. The welding tool 21 forces its way through the fluid part 53,moves toward the backing member 32, and is buried into the object 22.

The control means 46, for example, on the basis of the weldingconditions given in Table 1, gives a signal respectively to the drivingmeans 34 and 35, and when the welding tool 21 is buried up to apredetermined position, pressurizes the welding tool 21 at apredetermined pressure in the state that the welding tool 21 is rotated,and stirs the fluid part 53 formed in the object 22 around the weldingtool 21.

The control means 46, for example, on the basis of the weldingconditions given in Table 2, gives a signal respectively to the drivingmeans 34 and 35, and when the welding tool 21 is buried up to apredetermined position, stops the movement in the state that the weldingtool 21 is rotated, and stirs the fluid part 53 formed in the object 22around the welding tool 21.

Concretely, as shown in FIG. 7B, when the pin 51 reaches up to theneighborhoods of the respective boundary parts of the member 22 bnearest to the backing member among the members 22 a and 22 bconstituting the object to be welded 22, and of the member 22 a on theopposite side to the backing member 32, the control means 46 gives apredetermined pressure to the welding tool 21 in the state that it isrotated and stirs the fluid part 53. Or, the control means 46 stops themovement of the welding tool 21 in the state that it is rotated andstirs the fluid part 53. The welding tool 21 mixes the respective areaswhere the members 22 a and 22 b are neighboring. The control means 46,when the fluid part 53 is sufficiently stirred, goes to Step b5.

At Step b5, the control means 46, on the basis of the weldingconditions, gives a signal to the tool rotation driving means 34 and thetool movement driving means 35 and separates the welding tool 21 fromthe object 22. As shown in FIG. 7C, the welding tool 21 moves so as toseparate from the object 22 by the tool movement driving means 35. Thecontrol means 46, when it judges that the welding tool 21 moves up to apredetermined position, goes to Step b6.

At Step b6, the control means 46 gives a signal to the tool rotationdriving means 34, stops the rotation of the welding tool 21, and goes toStep b7.

At Step b7, the control means 46 finishes the operation relating to thewelding operation.

At Step b3, the control means 46, when it judges that the welding tool21 is not in contact with the object 22, goes to Step b8. At Step b8,the control means 46 controls the error lamp 43 so as to light and goesto Step b9. At Step b9, the control means 46 gives a signal to the toolrotation driving means 34 and the tool movement driving means 35 andmoves the tool holding jig 29 and the welding tool 21 respectively topreset initial positions. When the tool holding jig 29 is moved to theinitial position, the control means 46 goes to Step b10.

At Step b10, the control means 46 controls the error lamp 43 so as to goout. When the error lamp 43 goes out, the control means 46 goes to Stepb7. At Step b7, the control means 46 finishes the operation relating tothe welding operation.

The control means 46, during execution of the operation relating to thewelding operation, monitors an interruption of a signal given from theoperation pedal 39 and when a welding stop instruction signal is givenfrom the operation pedal 39 during the welding operation, goes to Stepa10 mentioned above. Further, the aforementioned operation of the toolholding jig 29 by the control means 46 is decided by the weldingconditions and when the welding conditions are changed, the operation ofthe control means 46 is also changed.

FIG. 8 is a flow chart showing the operation procedure of the controlmeans 46 of the welding position confirmation operation. The frictionstir welding apparatus, when the welding position confirmation operationis performed, can make an operator confirm the welding position wherethe object 22 is to be welded. The control means 46, when a signalindicating execution of the welding position confirmation operation bythe operator is given from the input unit 36, goes to Step c1 and startsthe operation of the control means 46 of the welding positionconfirmation operation.

At Step c1, the control means 46 gives a signal to the tool movementdriving means 35 so as to bring the tool holding jig 29 close to theobject 22 on the basis of the welding conditions. The control means 46,on the basis of the plate thickness of the object 22 and the length ofthe pin 51 and the tool 52, sets the movement distance of the weldingtool 21. When the movement of the welding tool 21 is completed, thecontrol means 46 goes to Step c2.

At Step c2, the control means 46 stops the welding tool 21 at theposition where it is close to the object. 22. By doing this, theoperator can confirm the position where the welding tool 21 will makecontact with the object 22. When a signal indicating that the operatorconfirms the welding position is given to the input unit, the controlmeans 46 goes to Step c3.

At Step c3, the control means 46 gives a signal to the tool movementdriving means 36 so as to separate the tool holding jig 29 from theobject 22 and moves the tool holding jig 29 to the predetermined initialposition. When the tool holding jig 29 is returned to the initialposition, the control means 46 goes to Step c4 and finishes theoperation. The aforementioned operation of the control means 46 isperformed without the tool holding jig 29 being rotated. However, thetool holding jig 29 may be rotated.

As mentioned above, in the friction stir welding apparatus 20 of thisembodiment, the base 23 is fixed to the floor 30 and the friction stirwelding apparatus 20 performs the welding operation for the object 22 inthe state that it is positioned with respect to the reference axis L1.Therefore, there is no need to move the base 23 for the object 22 andthere is no need to install an arm for moving the base 23. By doingthis, the constitution of the friction stir welding apparatus 20 can besimplified and miniaturized and an inexpensive friction stir weldingapparatus 20 can be provided. Further, the base 23 does not move, sothat the installation space can be made smaller.

As mentioned above, the friction stir welding apparatus 20 of thisembodiment can be manufactured under the condition of a smallinstallation space and a low cost, so that the initial fund necessaryfor introduction of the friction stir welding apparatus 20 can bereduced. Therefore, even a user who is short of funds and has only asmall installation space such as a small and medium-sized enterprise canintroduce the friction stir welding apparatus 20. When the friction stirwelding apparatus 20 is introduced and the object 22 is welded by thefriction stir welding, even if a heat treatment alloy having no moltenpart is used, a welded object having large welding strength and havinglittle strain and residual stress can be formed. Further, there is noneed to use a melting material and to remove excess metal, thus weldingcan be executed easily. Further, a welded object having a part to bewelded 47 whose quality is stable can be manufactured. Furthermore, evena material, a casting, a composite material, or a different kind ofmaterial which is easily cracked due to welding can be welded.

Further, the operator positions the object 22 and performs the weldingoperation, so that even if the shape of the object 22 is changed, thereis no need to teach the movement position of the welding apparatusunlike the conventional art. Therefore, the adjustment operation to beperformed for every object to be welded can be reduced and the timerequired for adjustment of the friction stir welding apparatus 20 can beshortened. Particularly when the object 22 is of low-volume andhigh-variety production, the adjustment time required for every objectto be welded can be reduced, thus the productive efficiency can beimproved.

Further, when the object 22 is supported and held by the backing member32, at the time of making contact with the welding tool 21, the part tobe welded 47 of the object 22 can be clamped by the backing member 32and the welding tool 21, and the part to be welded 47 of the object 22can be prevented from deformation. Further, since the reference axis L1is arranged vertically, the operator for positioning the object 22 mayload the object 22 on the backing member 32 and during welding, thereby,the weight of the object 22 is not applied to the hands of the operator.

Further, since the welding conditions can be input to the controller 38,the welding operation can be performed under different conditions forevery object 22 and the welding quality can be improved. The controlleris installed in the neighborhood of the base 23 and when an operatorperforms the welding operation, it is installed within his reach when hestretches his arm and at a position where there is no danger even if heoperates the input unit 36 during his welding operation. Therefore,during the welding, he can safely input the welding conditions to theinput unit 36.

Further, when the operation pedal 39 is stepped on by an operator, thecontrol means 46 controls so as to perform the welding operation, sothat when he leaves the base 23, the welding operation does not proceedand a failure in the operatorless state can be prevented.

Further, since the control means 46 judges whether the welding tool 21and the object 22 make contact with each other or not, it can notify anerr of positioning of the object 22. An err of positioning, for example,when the object 22 is not held by the base 23, is a case that thewelding position is a position different from a preset position.

Further, the control means 46 can perform the welding positionconfirmation operation for confirming the welding position to weld theobject 22 by an operator, so that the operator can fit the weldingposition accurately to the reference axis L1, thus the welding positioncan be prevented from shifting.

Further, the operator can instruct start and end of the weldingoperation by the operation pedal 39, so that he can perform the weldingoperation in the state that the object 22 is held by both hands duringthe welding operation. By doing this, the object 22 can be preventedfrom insufficient holding and from defective welding.

Further, since the operator is notified of the operation state by theend lamp 42, the error lamp 43, and the speaker 44, the operator canaccurately know the operation state and the operator can be preventedfrom his malfunctions.

FIG. 9 is a drawing showing another operation configuration of thefriction stir welding apparatus 20. For the friction stir weldingapparatus 20, the object to be welded 22 may not be positioned by anoperator and for example, the object 22 may be positioned for the base23 by a robot 600 holding the object 22. For example, when the object 22held by the robot 600 is to be sequentially processed by a plurality ofprocessing devices, the object 22 can be welded in the state that it isheld by the robot 600.

FIG. 10 is a drawing showing still another operation configuration ofthe friction stir welding apparatus 20 a, 20 b, and 20 c. As shown inFIG. 10, a plurality of friction stir welding apparatuses 20 a, 20 b,and 20 c mentioned above may be installed. On each of the friction stirwelding apparatuses 20 a, 20 b, 20 c, welding tools 21 a, 21 b, and 21 cin different shapes are mounted. The friction stir welding apparatuses20 a, 20 b, and 20 c performing the welding operation for every object22 are selected and by the friction stir welding apparatus having amounted welding tool according to the object 22, the welding operationis performed. By doing this, the labor for exchanging the welding tool21 according to the object 22 is saved, thus the productive efficiencycan be improved.

FIG. 11 is a side view showing a friction stir welding apparatus 120 ofanother embodiment of the present invention and FIG. 12 is a plan viewshowing the friction stir welding apparatus 120. The friction stirwelding apparatus 120 shown in FIGS. 11 and 12 has the same constitutionas that of the friction stir welding apparatus 20 shown in FIG. 1 exceptthe table, and the same reference numerals are assigned and theexplanation is omitted for the same portions.

The friction stir welding apparatus 120 includes a table 125 opposite tothe head 24 at an interval. The table 125 has a table body 125 a, abacking member support part 125 b, and a backing member 132. The tablebody 125 a is connected to the column 26 and is projected toward thereference axis L1 of the tool holding jig 29. On the face of the tablebody 125 a opposite to the tool holding jig 29, the backing membersupport part 125 b is installed. In the backing member support part 125b, a through hole 126 extending perpendicularly to the reference axis L1and in the radial direction of the reference axis L1 is formed.

The backing member 132 has a first part 133 which is formed in acylindrical shape and extends linearly and a second part 134 which isconnected to one end of the first part 133 so as to be bent from thefirst part 133 so that the backing member 132 forms a substantiallyL-shape. The second part 134 is fit into the through hole 126 of thebacking member support part 125 b. By doing this, the backing member 132is supported by the backing member support part 125 b. Further, in thefirst part 133, the center axis extending in the longitudinal directionthereof is arranged coaxially with the reference axis L1 and isprojected from the second part 134 toward the tool holding jig 29.Therefore, the second part 134 of the backing member 132 is projectedfrom the table body 125 a toward the reference axis L1 and the firstpart 133 is projected from the second part 134 toward the tool holdingjig 29.

Further, the base part 27 is connected removably to the floor by ananchor bolt 27 a.

During the friction stir welding, the welding operation is performed inthe state that the object 22 clamped and held by an operator or a robotis supported by the first part 133 of the backing member 134.

Also in the friction stir welding apparatus 120 of this embodiment, thesame effects as those of the friction stir welding apparatus 20 shown inFIG. 1 can be obtained. Furthermore, since the backing member 133 isformed almost in an L-shape and is projected from the table body 125 a,to position the object 22, the object 22 and the table body 125 a can beprevented from making contact with each other, and the table body 125 acan be prevented from obstructing the welding operation, thus a goodwelding operation can be performed.

FIG. 13 is a perspective view showing a friction stir welding device 220of still another embodiment of the present invention and FIG. 14 is aperspective view showing a holding jig 228 mounted on the friction stirwelding device 220.

The friction stir welding device 220 has the same constitution as thatof the friction stir welding apparatus 20 shown in FIG. 1 except thetable, and the same reference numerals are assigned and the explanationis omitted for the same portions.

In the friction stir welding device 220, the welding operation isperformed in the state that the holding jig 228 for holding the object22 is positioned on the table 225.

On the base 23 of the friction stir welding device 220, a table 226opposite to the head 24 is installed at an interval. The table 225 hasan opposing face 231 which is perpendicular to the reference axis L1 andfaces the tool holding jig 29. Further, on the table 225, a positioningmeans for positioning the holding jig 228 is installed. According tothis embodiment, the positioning means is composed of a plurality ofpositioning convexities 233 projecting from the opposing face 231 towardthe tool holding jig 29.

As shown in FIG. 14, the holding jig 228 holds the object 22. Theholding jig 228 is loaded on the opposing face 231 of the table 225. Inthe holding jig 228, positioning concavities 280 to be fit into thepositioning convexities 233 of the base 23 are formed. The holding jig228 is positioned so that the positioning concavities 280 are fit intothe positioning convexities 233 of the base 23.

The holding jig 228 is loaded on the opposing face 231 and includes asupport body 250 formed in a plate shape, a fixed piece 251 projectedfrom the face of the support body 250 on one side A1 in the thicknessdirection, and a holding part 252 having a pressing part 262 to whichforce toward the other side A2 in the thickness direction of the supportbody 250 is applied.

The face of the support body 260 on one side A1 in the thicknessdirection is a contact face 253 with which the object 22 is to makecontact. Further, the face of the support body 250 on the other side A2in the thickness direction is an apparatus contact face 290 which makescontact with the opposing face 231 of the table 225. The positioningconcavities 280 fitting into the plurality of positioning convexities233 formed in the table 255 are formed in the support body 250. In thestate that the object 22 is arranged in the support body 250, thepositioning concavities 280 are positioned so as to be fit into thepositioning convexities 233, thus the positioning concavities 280 areformed so that the object 22 is positioned for the base 23.

A plurality of fixed pieces 251 are installed. The fixed pieces 251,when the object 22 is arranged in the position to be held on the supportbody 250, make contact with faces 260 a and 260 b of the object 22 onthe side of the movement prevention direction B1 which is at least oneof the directions perpendicular to the thickness directions A1 and A2 ofthe support body 250. The fixing pieces 251 make contact with the object22 to prevent the object 22 from moving in the movement preventiondirection B1.

In this embodiment, each of the fixed pieces 251 is bent and extended inan almost L-shape and is composed of a first part 254 extending in onedirection A1 of the thickness direction of the support 255 from thecontact face 253 and a second part 255 which is connected to the end ofthe first part 254 and extends in the direction D2 opposite to themovement prevention direction B1.

For example, when the members 22 a and 22 b constituting the object 22are different in size and the faces 260 a and 260 b of the object 22 inthe movement prevention direction B1 are formed in a multi-stage, withthe face 260 b most projecting in the movement prevention direction B1among the multi-stage faces 260 a and 260 b, the first part 254 of thefixed piece 251 makes contact, and with the cave-in face 260 a in theopposite direction B2 of the movement prevention direction B1 from theface 260 b, an end face 261, which is an end face of the second part 255and is opposite to the part extended to the first part 254, makescontact.

Further, the holding part 252, for example, is realized by a toggleclamp. The toggle clamp includes a link mechanism composed of three linkbars 270, 271, and 272. The three link bars 270, 271, and 272 arearranged so as to change the angle almost on the same plane. The firstlink bar 270 and second link bar 271 are arranged so as to change theangle at one ends 270 a and 271 a and arranged so as to mutually cross.In the third link bar 272, both ends 272 a and 272 b are connected tomedium parts 270 b and 271 b of the first and second link bars 270 and271 in the longitudinal direction so as to change the angle. When thesecond link bar 271 changes the angle about the one end 271 a, the firstlink bar 270 intersecting it orthogonally changes the angle in the samedirection as the angle changing direction of the second link bar 271.

The first link bar 270 is arranged almost perpendicularly to thethickness directions A1 and A2 and is formed with the pressing part 262at its free end. The pressing part 262 is arranged facing to the portionsurrounding the part to be welded 47 where the object 22 is to bewelded. The pressing part 262 is formed, for example, in a C shape andfaces on the peripheral part of the object 22 in the peripheraldirection around the part to be welded 47. Further, the first link bar270 has a connected spring 273 and spring force for moving the pressingpart 262 in the other thickness direction A2 is given by the spring 273.Further, the second link bar 271 is arranged almost perpendicularly tothe thickness directions A1 and A2 and a holding part 281 for anoperator to hold the second link bar 271 is installed at the free endpart.

The holding part 281 is arranged at the position in the neighborhood ofthe pressing part 262 by the spring 273 in the natural state. Theoperator holds the holding part 281 and changes the angle of the secondlink bar 271 in the direction to separate the pressing part 262 from thesupport body 250, thus the pressing part 262 is separated from thesupport body 250 and a gap for making the object 22 contact with thesupport body 250 is formed.

The object 22 is made contact with the contact face 253 of the supportbody 250 by the operator. The object 22, in the state in contact withthe contact face 253 of the support body 250, is moved in the movementprevention direction B1 toward the fixed piece 251 and the object 22makes contact with the fixed piece 251 so as to be positioned.

In this state, the operator moves the holding part 281 in the directionto bring it close to the support body 250. The pressing part 262approaches the support body 250 by the elastic recovery force of thespring 273. The pressing part 262 presses the object 22 in the otherthickness direction A2 and the object 22 is clamped and held by thepressing part 262 and the support body 250.

In the state that the object 22 is held, the holding jig 228 ispositioned so as to fit the positioning concavities 280 of the holdingjig 282 into the positioning convexities 233 of the base 23. By doingthis, the object 22, which is held by the holding jig 228, can bepositioned to the base 23.

Also in the friction stir welding device 220 in this embodiment, thesame effects as those of the friction stir welding apparatus 20 shown inFIG. 1 can be obtained. Furthermore, since the positioning concavities280 of the holding jig 282 are fit into the plurality of positioningconvexities 233, when the operator moves and positions the object 22 tothe base 23, the object 22 can be prevented from shifting. By doingthis, the time required to adjust the position of the object 22 to thebase 23 can be shortened and the number of objects 22 to be welded perunit time can be increased.

Further, the holding jig 228 for holding the object 22 is positioned tothe base 23, thus the welding operation can be performed in the statethat the object 22 to be positioned to the reference axis L1 is held,The welding operation is performed in the state that the object 22 isheld, thus the object 22 can be prevented from shifting, movement, anddeformation during welding. By doing this, the welding quality of theobject 22 can be improved.

Further, when the welding tool 21 is to rotate and make contact with theobject 22, there is the possibility that force to move the object 22 maybe applied and the object 22 may be raised to high temperature byfrictional heat. The welding operation is performed in the state thatthe holding jig 228 holds the object 22, thus the operator himself doesnot need to hold the object 22 and the convenience is enhanced.

Further, in the holding jig 228, the fixed pieces 251 are formed in analmost L shape, so that even when the plurality of members 22 a and 22 bconstituting the object 22 are different in size, they be can be heldsurely. Further, in the state that the holding jig 288 is mounted in thefriction stir welding device 220, it is possible to position the object22 to the holding jig 228 and hold the object 22 by the holding jig 288.Further, the object 22 held by the holding jig 228 is positioned so thatthe part to be welded 47 is arranged on the reference axis L1, thus thepositioning operation of the object 22 can be performed easily.

Further, the circumference of the part to be welded 47 of the object 22is clamped by the clamping part 252, thus a gap can be prevented frombeing formed between the plurality of members 22 a and 22 b constitutingthe object 22 and the part to be welded 47 of the object 22 can be madecontact with the support body 250. Further, the constitution of theholding jig 228 is not limited to the constitution shown in FIG. 14 andany other constitution capable of holding the object 22 is acceptable.

FIG. 15 is a perspective view showing a holding jig 328 of anotherexample and FIG. 16 is a perspective view showing a clamping part 352 ofthe holding jig 328.

The holding jig 328 is mounted on the opposing face 231 of the table225. In the holding jig 328, positioning concavities 380 to be fit intothe positioning convexities 233 of the base 23 are formed. Thepositioning concavities 380 of the holding jig 328 are fit into thepositioning convexities 233 of the base 23, thus the holding jig 328 ispositioned.

The holding jig 328 is mounted on the opposing face 231 and includes asupport body 350 formed in a plate shape and clamping parts 352 havingpressing parts 362 for pressing the object 22 in the other thicknessdirection A2 of the support body 250.

The face of the support body 350 on one side A1 in the thicknessdirection is a contact face 353 with which the object 22 makes contact.Further, the face of the support body 350 on the other side A2 in thethickness direction is an apparatus contact face 390 which makes contactwith the opposing face 231 of the table 225. The positioning concavities380 to be fit into the plurality of positioning convexities 233 formedin the table 255 are formed in the support body 350. In the state thatthe object 22 is arranged on the support body 360, the positioningconcavities 380 are formed so that the object 22 is positioned to thebase 23.

In the support body 350, a plurality of rail grooves 351 extending alongthe rail directions C1 and C2 perpendicular to the thickness directionsA1 and A2 are formed. The rail grooves 351 are open in one thicknessdirection A1 and when the support body 350 is cut on the planeperpendicular to the rail directions C1 and C2, an area becoming smalleras extending in one thickness direction A1 is formed.

For example, when cut on the plane perpendicular to the rail directionsC1 and C2, the rail grooves 351 are formed in an almost inverse T-shape.Concretely, in the rail grooves 351, on the opening side, narrow areas351 a are formed and on the other side A2 in the thickness directionfrom the narrow areas 351 a, wider areas 351 b wider than the narrowareas 351 a are formed.

As shown in FIG. 16, each clamping part 352 includes the pressing part362 for pressing the object 22, a screw rod 364 inserted into thepressing part 362, and a screwed part 363 spirally attached to the screwrod 364. The pressing part 362 has an insertion part 362 a having ascrew rod insertion hole into which the screw rod 364 is inserted, and aclamping part 362 b projected perpendicularly to the axis of theinsertion hole from the insertion part 362 a. The screw rod 364 has ahead 365 larger than the screw rod insertion hole formed at an end 364 athereof. Further, the screwed part 363 is screwed to another end 364 bof the screw rod 364 and moves up and down. The screwed part 363 is fitinto the wide area 351 a of the rail groove 351. Further, the screw rod364 is inserted into the pressing part 362, inserted into the narrowarea 351 b of the rail groove 351 a, and is screwed to the screwed part363.

When the screw rod 364 rotates, the screwed part 363 approaches orseparates from the head 363 of the screw rod 364. The screwed part 363is fit into the rail groove 351, so that it will not come out from therail groove 351, and the screw rod 364 rotates, thus the pressing part362 approaches or separates from the support body 350.

FIG. 17 is a perspective view showing the friction stir welding device220 in the state that the holding jig 328 is mounted and FIG. 18 is asectional view viewed from the section line S-S shown in FIG. 17. In thestate that the object 22 is mounted on the support body 350, theplurality of clamping parts 352 are arranged on the peripheral part ofthe object 22. In each clamping part 352, the clamping part 362 a of thepressing part 362 is fixed to the surface on one side A1 in thethickness direction of the object 22.

When the screw rod 364 rotates in this state, the pressing part 362moves toward the support body 350 and presses the object 22 to thesupport body 350. The object 22 is clamped, thus the object 22 isprevented from moving perpendicularly to the thickness directions A1 andA2, thereby can be held. Further, the shape of the pressing part 362 canbe changed according to the shape of the object 22, thus the object 22can be suitably clamped. The object 22 is held by the holding jig 328 inthe positioned state. By doing this, the part to be welded 47 of theobject 22 is arranged on the reference axis L1.

The holding jig 328 is prepared for every object 22 and it stands by inthe state that it holds the object 22. An operator arranges the holdingjig 328 holding the object 22 on the friction stir welding apparatus 320and starts the welding operation. When the welding operation iscompleted, he removes the object 22 together with the holding jig 328.By doing this, there is no need to directly position the object 22 onthe base and the welding operation can be shortened. Further, theclamping part 352 slides along the rail groove 351, thus even an object22 different in size can be held by one holding jig 328.

The friction stir welding device 220, when the holding jig 328 ispositioned, can obtain the same effects as those when the holding jig228 shown in FIG. 14 is positioned, and the operator does not need tohold the object 22, and the convenience can be enhanced. As mentionedabove, a holding jig 228 according to the kind of the object 22 may beprepared and a holding jig 328 for holding each object to be welded 22may be installed. Further, when the object 22 is retained in the statethat it is held by the holding jig 328, the positioning operation in thewelding operation can be shortened and the time required for the weldingoperation can be shortened.

FIG. 19 is a perspective view showing still another holding jig 528. Theholding jig 528 is temporarily fixed to the object 22 at one or morepositions. The holding jig 528 is fixed at the position facing on thewelding position of the object 22 in contact with the object 22 from theopposite side of the tool holding jig 29. On the holding jig 528, afitting part 529 fitting into the positioning means of the base 23 isformed. For example, when the positioning means of the base 23 is pinholes formed in the table, the fitting part 529 has projections formedso as to be fit into the pin holes.

The fitting part 529 of the holding jig 528 and the pin holes of thetable are formed so that the object 22 can be positioned to the base 23by fitting the fitting part 529 into the pin holes in the state that theholding jig 528 is temporarily fixed to the object 22.

Using the friction stir welding device 220, the welding operation isperformed in the state that the holding jig 528 temporarily fixed to theobject 22 is positioned on the table. The holding jig 528, at theposition facing on the welding part, is fixed in contact with the object22 from the opposite side of the tool holding jig 29. By doing this,when the welding operation is performed, the object 22 can be supportedby the holding jig 528 from the opposite side of the welding tool 21,and the object 22 is prevented from deformation, thus the weldingoperation can be performed satisfactorily. Namely, the object to bewelded 22 is positioned by the holding jig 528 and the same effects asthose when the backing member 32 shown in Table 1 is used can beobtained.

Further, the shape of the fitting part 529 may be any other shapes whichare positioned by the positioning means of the table.

Further, when a face 530 of the holding jig 528 which makes contact withthe object 22 is formed along the shape of the object 22, even if theobject 22 has a curved surface or a three-dimensional surface, it can besupported satisfactorily.

Further, also with respect to the other holding jigs 228 and 328mentioned above, when the object 22 is supported at the position facingon the welding position in contact with the object 22 from the oppositeside of the tool holding jig 29, the same effects as those when thebacking member 32 is used can be obtained.

FIG. 20 is a perspective view showing the friction stir weldingapparatus 420 of a further embodiment of the present invention and FIG.21 is a sectional view showing the enlarged neighborhood of the table ofa friction stir welding apparatus 420. The constitution of the frictionstir welding apparatus 420 is the same as that of the friction stirwelding apparatus 20 shown in FIG. 1 except the head and table, and thesame numerals are assigned and the explanation will be omitted for thesame portions.

The base 23 of the friction stir welding apparatus 420 includes a head424 where the tool holding jig 29 for removably mounting the weldingtool 21 is installed and a table 425 facing the head 424 at an interval.The table 425 has an opposing face 431 which is perpendicular to thereference axis L1 and facing the tool holding jig 29. On the table 425,the columnar backing member 32 projecting from the opposing face 431toward the tool holding jig 29 is installed. Furthermore, on the head424 and the table 425, a holding means 428 for holding the object 22 isinstalled.

The holding means 428 includes a first clamping piece 450 and a secondclamping piece 451 which cooperatively clamp the object 22, a clampingpiece movement driving means 452 for moving the first clamping piece450, and a spring force generation means 453 for elastically supportingthe second clamping piece 461.

The first clamping piece 450 is installed on the head 424 movably alongthe reference axis L1 and is arranged in the peripheral direction of thetool holding jig 29. The clamping piece movement driving means 452 movesthe first clamping piece 450 so as to displace relatively with respectto the tool holding jig 29 and the base 23 along the reference axis L1.The clamping piece movement driving means 452 operates according to asignal given from the control means 46.

The second clamping piece 451 is installed on the table 425 movablyalong the reference axis L1 and is arranged in the peripheral directionof the backing member 32. The second clamping piece 451 is projectedtoward the tool holding jig 29 over an end face 455 of the backingmember 32 at the initial position in the no-load state when the object22 is not arranged and is elastically supported by the spring forcegeneration means 453. The spring force generation means 453 gives springforce for moving the second clamping piece 451 toward the tool holdingjig 29 along the reference axis L1, and for example, it is realized byan air damper or a compression coil spring. Further, the first clampingpiece 450 and the second clamping piece 451 are arranged in oppositepositions and it is preferable to form them at a plurality of locationsaround the reference axis L1 or to form them over a wide range.

According to this embodiment, the first clamping piece 450 is formed ina cylindrical shape so as to cover the tool holding jig 29 in theperipheral direction thereof. The first clamping piece 450 is arrangedcoaxially with the tool holding jig 29. The second clamping piece 451 isformed in a cylindrical shape so as to cover the backing member 32 inthe peripheral direction thereof. The second clamping piece 451 isarranged coaxially with the tool holding jig 29. When the first andsecond clamping pieces 450 and 451 are cylindrical, the outer diameterD1 of the second clamping piece 451 is larger than the inner diameter D2of the first clamping piece 450 and the inner diameter D3 of the secondclamping piece 451 is smaller than the outer diameter D4 of the firstclamping piece 450.

Further, the shape of the first and second clamping pieces 450 and 451is not limited to cylindrical and it may be hollow.

The second clamping piece 451, when force of pressing toward below thereference axis L1 is applied against the spring force of the springforce generation means 453, shifts in the pressing direction. An endface 454 of the shifting second clamping piece 451 on the tool holdingjig side is arranged on the same level as that of the end face 455 ofthe backing member 32 on the tool holding jig side or at a positionwhere it is shifted more than the backing member 32.

FIGS. 22A, 22B, and 22C are sectional views showing the operation of theholding means 428. As shown in FIG. 22A, on the end face 454 of thesecond clamping piece 451 on the tool holding jig side, the object 22 isarranged. The object 22, in the state that the part to be welded 47 ispositioned by an operator so as to be arranged on the reference axis L1,is arranged on the second clamping piece 451. The second clamping piece451 is arranged in the no-load state in the initial position when it isprojected more than the backing member 32, so that the object 22arranged on the second clamping piece 461 is arranged in the directionof the reference axis L1 at an interval from the backing member 32.

When the welding operation is started, the clamping piece driving means452 receiving a signal from the control means 46 moves the firstclamping piece 450 toward the backing member 32. The first clampingpiece 450 moves toward the backing member 32 along the reference axisL1, thereby makes contact with the object 22 arranged on the secondclamping piece 451.

The first clamping piece 450, in the state in contact with the object22, additionally moves toward the backing member 32. The first clampingpiece 450 moves against the spring force of the spring force generationmeans 453 for elastically supporting the second clamping piece 451.Therefore, the object 22 moves toward the backing member 32 in the statethat it is clamped by the first clamping piece 450 and the secondclamping piece 451.

As shown in FIG. 22B, in the state that the object 22 clamped and movingmakes contact with the backing member 32, the clamping piece drivingmeans 452 stops the movement of the first clamping piece 450. Forexample, when the control means 46 judges by a contact sensor that theobject 22 makes contact with the backing member 32, it gives a signal tothe clamping piece driving means 452 and stops the operation of theclamping piece driving means 452.

The first and second clamping pieces 450 and 451 cooperatively clamp andhold the object 22, prevent the object 22 from moving along thereference axially line L1, applying no excessive load causingdeformation to the object 22, thereby can support the object 22 by thebacking member 32. In the state that the object 22 is held free ofdeformation and supported by the backing member 32 like this, thewelding operation shown in FIG. 5 is executed. By doing this, as shownin FIG. 22C, the welding tool 21 is buried in the object 22 and thefriction stir welding operation is performed.

The control means 46, upon receipt of a welding start instructionsignal, gives the signal to the clamping piece movement driving means452 and moves the first clamping piece 450 toward the backing member 32.The control means 46, on the basis of a load torque signal from thecontact sensor or the clamping piece movement driving means 452, judgeswhether the object 22 makes contact with the backing member 32 or not.And, when the control means 46 judges that the object 22 makes contactwith the backing member 32, it give a signal to the clamping piecemovement driving means 452 and stops the movement of the first clampingpiece 450. Further, when the control means 46 judges that the weldingoperation is completed, it gives a signal to the clamping piece movementdriving means 452 and moves the first clamping piece 450 so as toseparate from the backing member 32.

FIGS. 23A and 23B are sectional views showing holding means 500 of acomparison example different from the holding means 428 of thisembodiment. The holding means 500 of the comparison example clamps andholds the object 22 without being supported elastically in the axialdirection L1. By use of such a constitution, as shown in FIG. 23A, whenthe object 22 is deformed, the holding means 500 cannot support the partto be welded 47 by the backing member 32 in the state that the object 22is clamped. When the friction stir welding is executed in this state,the welding tool 21 makes contact with the tip of the object 22 in thestate that it is not supported by the backing member 32. Therefore, asshown in FIG. 23B, there is the possibility that the part to be welded47 may be deformed and the welding tool 21 may be buried in the object22 more than a preset value and a problem arises that satisfactorywelding cannot be executed.

On the other hand, in this embodiment shown in FIG. 21, the apparatus isstructured so that the second clamping piece 451 is projected from theend face 455 of the backing member 32 on the tool holding jig sidetoward the tool holding jig 29 and is moved elastically along thereference axis L1 and at the point of time when the object 22 makescontact with the backing member 32 by the contact sensor, the, movementof the first clamping piece 450 can be stopped, so that failures asshown in FIGS. 23A and 23B will not be caused.

Namely, in this embodiment shown in FIG. 21, in the state that theobject 22 is kept and held in the natural shape free of an excessiveload causing deformation, the part to be welded 47 of the object 22 canbe supported by the backing member 32. When the part to be welded 47 issupported by the backing member 32, the part 47 is prevented fromdeformation, and the welding tool 21 can be prevented from being buriedin the object 22 by more than the preset value, thus satisfactorywelding can be executed. Further, since the object 22 is held by thefirst and second clamping pieces 450 and 451, the members 22 a and 22 bconstituting the object 22 can be prevented from shifting duringwelding.

Also in the friction stir welding apparatus 420 mentioned above, thesame effects as those of the friction stir welding apparatus 20 shown inFIG. 1 can be obtained. Furthermore, the welding operation can beperformed in the state that the object 22 is kept and held in thenatural shape by the holding means 428. By doing this, the object 22 canbe prevented from deformation and displacement during welding, and thewelding quality can be improved.

Further, the welding operation can be performed in the state that theobject 22 is clamped by the first clamping piece 450 and the secondclamping piece 451 and additionally is moved and supported by thebacking member 32. By doing this, clamping of the object 22 andsupporting of the part to be welded 47 can be realized simultaneouslyand the welding quality can be more improved. Further, the firstclamping piece 450 makes contact with and separates from the object 22by the clamping piece movement driving means 452, thus the object 22 canbe switched to the holding state or the release state, and the holdingoperation and release operation thereof can be easily performed.

Further, the part to be welded 47 and the welding tool 21 are covered bythe first clamping piece 450 and the second clamping piece 451, so thatduring welding, the fluid object 22 can be prevented from scattering,and the operator can work safely. Even if the part to be welded 47 andthe welding tool 21 are covered and the working state cannot be seen,the friction stir welding apparatus 420 can notify the operator of theworking state since the end lamp 42 and the error lamp 43 notify anoperator of the end of the welding operation and an error

Further, when the parts of the first clamping piece 450 and the secondclamping piece 451 which are opposite to each other are composed of aflexible and elastic material, even if a shape error of the object 22 islarge, the object 22 can be clamped closely and surely. Further, thefirst clamping piece 450 and the second clamping piece 451 may bestructured so as to exchange the first clamping piece 450 and the secondclamping piece 451 according to the shape of the object 22. Further, thefirst and second clamping pieces 450 and 451 do not need to be formedcylindrically and they may be in other shapes.

Further, a spring force generation means for giving spring force forpressing the tool holding jig 29 and the first clamping piece 450 towardthe backing member 32 can be installed. In this case, the first clampingpiece 450 is arranged so that the end face 466 on the backing memberside is projected toward the backing member 32 in the no-load state overthe end of the tool holding jig 29. The spring force given to the firstclamping piece 450 by the spring force generation means for the firstclamping piece 450 is set larger than the spring force given to thesecond clamping piece 451 by the spring force generation means for thefirst clamping piece 451. The first clamping piece 450 is moved alongthe reference axis L1 together with the tool holding jig 29 withoutrotating about the reference axis L1. By doing this, the part to bewelded 47 of the object 22 makes contact with the backing member 32 inthe state that the object 22 is clamped and similarly to theaforementioned, the welding quality can be improved.

The friction stir welding apparatuses 20, 120, 220, and 420 mentionedabove are just examples of the present invention and the constitutioncan be changed within the range of the present invention. For example,the tool rotation driving means 34 and the tool movement driving means35 may be installed at a position away from the base 23. Further, thereference axis L1 is described as it extends vertically. However, it mayextend in any direction other than the vertical direction. Further, withrespect to the tool movement driving means 35, the tool holding jig 29may be moved along the reference axis L1, or the head 24 where the toolholding jig 29 is installed may be structured movably and may be movedalong the reference axis L1.

Further, in the above description, regarding the positioning means forpositioning the holding jigs 228 and 238 and the table 225, theconcavities 280 and 380 and the convexities 233 are installedrespectively on the holding jigs 228 and 238 and the table 225. However,the relationship of concavities and convexities may be inverted. Namely,convexities may be formed in the holding jigs 228 and 328 andconcavities may be formed in the table 225. Further, the concavities maybe formed in a rail shape.

Further, in the aforementioned embodiment, the tool holding jig 29, onwhich the welding tool 21 is mounted, is rotated and moved. However, asa deformed example, a constitution may be used that the friction stirwelding apparatus shown in FIG. 1 or 13 is partially changed, and thetool holding jig 29, on which the welding tool 21 is mounted, isrotated, and the backing member 32 is moved along the reference axis L1instead of moving the tool holding jig 29.

Namely, the friction stir welding apparatus in this example, as shown inFIG. 24 (and FIG. 1), includes the tool holding jig 29 mounted on thehead 24, on which the welding tool 21 is rotatably installed so as toface the table 25, the tool rotation driving means 34 for rotating thetool holding means 29 about the rotation axis, the backing member 32which is installed on the table 25 so as to move in the movementdirection to approach and separate from the tool holding jig 29, and abacking member movement driving means 35′ for moving the backing memberalong the reference axis L1. By use of such a constitution, there is noneed to arrange the tool movement driving means 35 on the head side andthe friction stir welding apparatus can be further miniaturized.

1. A friction stir welding apparatus configured to spot weld an object,comprising: a base fixed at a predetermined position; a tool holding jigto which a welding tool is mounted, said tool holding jig beinginstalled on said base rotatably about a reference axis and movablyalong said reference axis; tool rotation driving means for rotating saidtool holding jig about said reference axis; tool movement driving meansfor moving said tool holding jig along said reference axis; positioningmeans, which is installed on said base, for positioning an object to bewelded with respect to said reference axis; and holding means forholding said object to be welded with respect to said base, saidpositioning means positioning the holding means, wherein said holdingmeans has a backing member for supporting a part of said object locatedon said reference axis from a side opposite to said welding tool, andthe backing member and the tool holding jig remain axially alignedthroughout a spot welding process; and an operation pedal which outputsa welding start instruction from an operator.
 2. A friction stir weldingapparatus according to claim 1, wherein said holding means comprising: afirst clamping piece installed movably along said reference axis withrespect to said base and said tool holding jig; clamping piece movementdriving means for moving said first clamping piece along said referenceaxis; a second clamping piece for holding said object cooperatively withsaid first clamping piece, said second clamping piece being installed sothat said second clamping piece can move along said reference axis froma projection position projecting over said backing member and aretraction position retracting with respect to said backing member, andspring force generation means for giving spring force toward saidprojection position to said second clamping piece.
 3. A friction stirwelding apparatus according to claim 2, wherein: said first clampingpiece is formed so that a center axis thereof is coaxially with saidreference axis; said second clamping piece is formed so that a centeraxis thereof is coaxially with said reference axis; and said object isclamped by an end face of said first clamping piece and an end face ofsaid second clamping piece.
 4. A friction stir welding apparatusaccording to claim 3, wherein said first clamping piece and said secondclamping piece are formed in a cylindrical or hollow shape,respectively.
 5. A friction stir welding apparatus according to claim 4,wherein: said backing member is installed movably along said referenceaxis; and backing member movement driving means for moving said backingmember along said reference axis is installed in place of said toolmovement driving means.
 6. A friction stir welding apparatus accordingto claim 2, wherein: said backing member is installed movably along saidreference axis; and backing member movement driving means for movingsaid backing member along said reference axis is installed in place ofsaid tool movement driving means.
 7. A friction stir welding apparatusaccording to claim 3, wherein: said backing member is installed movablyalong said reference axis; and backing member movement driving means formoving said backing member along said reference axis is installed inplace of said tool movement driving means.
 8. A friction stir weldingapparatus according to claim 1, wherein: said backing member isinstalled movably along said reference axis; and backing member movementdriving means for moving said backing member along said reference axisis installed in place of said tool movement driving means.
 9. A frictionstir welding apparatus according to claim 1, wherein the positioningmeans, the holding means, and the backing member form a table forholding the object to be welded.
 10. A friction stir welding apparatusconfigured to spot weld an object, comprising: a base fixed at apredetermined position; a tool holding jig to which a welding tool ismounted, said tool holding jig being installed on said base rotatablyabout a reference axis and movably along said reference axis; toolrotation driving means for rotating said tool holding jig about saidreference axis; tool movement driving means for moving said tool holdingjig along said reference axis; and holding means, which is installed onsaid base, for holding an object to be welded, wherein said holdingmeans has a backing member for supporting a part of said object locatedon said reference axis from a side opposite to said welding tool, andthe backing member and the tool holding jig remain axially alignedthroughout a spot welding process; and an operation pedal which outputsa welding start instruction from an operator.
 11. A friction stirwelding apparatus according to claim 10, wherein the holding means andthe backing member form a table for holding the object to be welded.